1. Field of the Invention
The present invention relates to an oscillating internally meshing planetary gear reducer.
2. Description of the Related Art
Geared motors 1, and 2 and 2′ are conventionally known that are disclosed in Japanese Published Unexamined Patent Application Nos. 2002-106650 and 2002-122190 respectively.
FIG. 6 shows the geared motor 1 disclosed in Japanese Published Unexamined Patent Application No. 2002-106650. FIG. 7 shows the geared motor 2 disclosed in Japanese Published Unexamined Patent Application No. 2002-122190. FIG. 8 shows the geared motor 2′ disclosed in Japanese Published Unexamined Patent Application No. 2002-122190. The same reference symbols are attached to the same or similar parts of each geared motor respectively, and each geared motor will be described.
Each geared motor includes: a motor 10 which serves as a power source; a pinion or pulley 14 provided on a motor shaft 12 of the motor 10; an eccentric body shaft 30 provided with an eccentric body 32 for oscillating an oscillating external gear 34; and a carrier body 38 (38A, 38B) for taking out a rotation component of the oscillating external gear 34. The carrier body 38 is pivotably supported by a casing 40 via a carrier body bearing 50 (50A, 50B).
In the geared motor 1, the pinion 14 meshes with a distributing gear 26 having a large diameter, and a small gear 26A integrated with the distributing gear 26 meshes with input gears 20 provided on three eccentric body shafts 30 (only one shaft 30 appears in FIG. 6). Additionally, the distributing gear 26 is rotatably supported by bearings 80 and 81.
In the geared motor 2, the pinion 14 directly meshes with one of input gears 20 provided on the eccentric body shaft 30 (only one of the three eccentric body shafts 30 is shown in FIG. 7). The input gear 20 further meshes with the distributing gear 26, and the distributing gear 26 meshes with the other input gears 20 (both not shown) provided on the other eccentric body shafts 30 respectively. That is, the three eccentric body shafts 30 (30A, 30B and 30C) are arranged which are provided with the input gears 20 (20A, 20B and 20C) respectively, the input gear 20A meshes with the pinion 14 and the distributing gear 26, and the other input gears 20B and 20C mesh with only the distributing gear 26. Additionally, the distributing gear 26 is rotatably supported by the bearings 80 and 81.
In the geared motor 2′, the pulley (corresponding to the pinion) 14 is connected to an input pulley (corresponding to the input gear) 20 via a belt, and the input pulley 20 is fixed to the eccentric body shaft 30. An eccentric body shaft gear 28 is formed in the vicinity of the approximate center in an axial direction of the eccentric body shaft 30, and the eccentric body shaft gear 28 meshes with the distributing gear 26. Two eccentric body shafts 30 (not shown) are also used other than the shown shaft 30, and the eccentric body shaft gears 28 are formed on the two shafts 30 respectively to mesh with the distributing gear 26. However, the two eccentric body shafts 30 are provided with no input pulley 20. Additionally, the distributing gear 26 is rotatably supported by the bearings 80 and 81.
In a geared motor 1, rotation of a motor 10 is transmitted to all eccentric body shafts 30 via a distributing gear 26. The distributing gear 26 is constituted by a large gear to be meshed with a pinion 14 and a small gear 26A to be meshed with an input gear 20. The pinion 14 directly meshes with the distributing gear 26 of which an axis is largely gapped from that of the pinion 14, and thus a diameter of the distributing gear 26 unavoidably becomes large and a shape thereof becomes complicated, and there arises a problem in terms of cost.
In a process that the rotation of the motor 10 is transmitted to all the eccentric body shafts 30 in geared motors 2 and 2′, the pinion (pulley) 14 is meshed (connected) with the input gear (input pulley) 20 provided on one eccentric body shaft 30, and then the distributing gear 26 rotates with rotation of the eccentric body shaft 30, and the other eccentric body shafts 30 rotate with the rotation of the distributing gear 26. Thus, a diameter of the distributing gear 26 can be relatively made small. However, since the three eccentric body shafts 30 do not rotate at the same time, there arises a gap due to backlash which is not preferable in terms of precision. Additionally, since only a speed reduction rate in a meshing (connecting) part between the pinion (pulley) 14 and the input gear (input pulley) 20 can be obtained, a high speed reduction ratio can be hardly realized.